Various microactuators have been produced by using MEMS (Micro Electro Mechanical System) techniques, and applications of microactuators to various fields such as optics, high-frequency circuits, and biotechnology are expected. For example, in the field of adaptive optics, micromirror arrays for controlling the wave front of light are being developed. In such applications, in order to smoothly control the wave front of light, it is effective to cause each light reflecting surface to have a tilt as well as a vertical displacement relative to a base.
An example of a microactuator which is capable of such tilt and vertical displacement is disclosed in Non-patent Document 1. FIG. 10 is a perspective view schematically showing a microactuator 1000 disclosed in Non-patent Document 1.
The movable electrode 100 is supported at its outer periphery by three elastic beams 101a, 101b, and 101c. Moreover, the movable electrode 100 opposes three stationary electrodes 102a, 102b, and 102c. The stationary electrodes 102a, 102b, and 102c are provided in such a manner that a driving voltage can independently be applied to each of them, whereby a potential difference with the movable electrode 100 is obtained. As a result, an electrostatic force is generated in a direction of pulling the movable electrode 100.
If equal driving voltages are set for the stationary electrodes 102a to 102c, the movable electrode 100 makes a vertical displacement in the lower direction, without tilting. If these driving voltages are made different, the movable electrode 100 makes a vertical displacement in the lower direction while tilting in the desired direction. Thus, the movable electrode 100 is capable of making a vertical displacement in the lower direction as well as having a bi-axial tilt.
Since the mirror 103 is attached to the movable electrode 100 at an attachment section 104, the displacement of the movable electrode 100 in itself governs the displacement of the mirror 103.
Non-patent Document 1: U. Srinivasan, et al., “Fluidic Self-Assembly of Micromirrors Onto Microactuators Using Capillary Forces”, IEEE Journal on Selected Topics in Quantum Electronics, Vol. 8, No. 1, pp. 4-11 (January, 2002)